准噶尔盆地南缘一次强沙尘暴成因分析

Diagnosis of a Sandstorm Weather Event in the South of Junggar Basin

利用常规观测资料和T639 0场预报资料,对2009年4月13日发生在准噶尔盆地南缘石河子垦区一次强沙尘暴进行了天气成因分析。结果表明,这次强沙尘暴是西北路径较强冷空气引发的锋后偏西大风沙尘暴天气过程。前期持续高温少雨为沙尘暴的发生提供了有利的热力条件和一定的物质基础。西西伯利亚冷槽的斜压性结构使其强烈发展,为沙尘暴的发生提供了动力条件。而西西伯利亚冷槽的垂直结构强迫出一支下沉气流,为沙尘暴的发生提供了动量下传机制。高低空急流导致对流层中下部锋区加强和大气层结不稳定,为沙尘暴的产生提供了有利的中尺度条件。干暖舌的形成和维持对沙尘暴的发生以及落区有很好的指示性。沙尘暴发生在地面冷锋后部、冷高压前部以及3 h变压、变温最大处和低空气流辐散的地区。准噶尔盆地南缘的特殊地形和流沙为沙尘暴形成提供了有利的地理环境。

Based on the data of basic observation and numerical forecasting product T639, the causes of a sandstorm weather process occurred on April 13, 2009 in the south of Junggar Basin were analyzed. The results show it was caused by the north -west strong cold air. The continual temperature rising provided the favorable thermal condition for sandstorm, and the West Siberian cold trough moving towards southeast and developing greatly provided the dynamical condition for it. The vertical structure of Siberian cold trough provided the mechanism of momentum transmitting downwards for sandstorm. The upper and lower level jet stream made the frontal zone at the middle and lower troposphere strengthen and atmospheric stratification unstable, which provided a favorable large - scale circulation environment. The development and persistence of dry - warmer tongue was an omen for its occurrence. The strong sandstorm occurred in the rear of the cold front, the front of the cold high pressure and the airflow divergence zone. Moreover, the special terrain also provided a favorable geographical condition.